1. Field of the Invention
The present invention relates to a sheet feeder and a sheet feeding method, for plate-shaped members such as printing plates, which are taken out one-by-one from a state in which plate-shaped members and interleaf papers for protecting printing surfaces of the plate-shaped members are alternately stacked with one another.
2. Description of the Related Art
A technique has been developed, wherein a printing plate such as a photopolymer plate having a photosensitive layer (for example, a photopolymerization layer) provided on a support is used and an image is directly recorded on the photosensitive layer (photopolymerization layer) of the printing plate by a laser beam or the like (an automatic exposure apparatus for printing plates). In such a technique, an image can be rapidly recorded on the printing plate.
In the automatic exposure apparatus for printing plates for image recording on printing plates, a magazine accommodates a large number of printing plates in a stack, and the printing plates are removed from the magazine one-by-one and transferred to an exposure section.
There are cases in which the printing plates may be stacked with interleaf papers interposed therebetween so as to protect the printing surfaces of the plates. Due to the printing plates and the interleaf papers being alternately stacked with one another, scratching or the like of the light-sensitive layer and the support for a printing plate adjacent thereto, contacting each other, is substantially prevented.
On the other hand, in a sheet feeder, the uppermost printing plate within the magazine is taken out one-by-one with a sucker (suction cup). In the sheet feeder at this time, first the interleaf paper which covers the uppermost printing plate is taken out by suction. Thereafter, the uppermost printing plate is sucked to the sucker and removed from the magazine.
However, in this arrangement in which interleaf papers and printing plates are alternately stacked, an interleaf paper and a printing plate adjacent thereto can stick together. Therefore, there is a disadvantage in that when the interleaf paper is adhered to a sucker, a printing plate disposed immediately below the interleaf paper is lifted up together with the interleaf paper.
The present invention has been devised in view of the above-described circumstances, and an object thereof is to provide a sheet feeder in which when plate-shaped members such as printing plates and sheet materials such as interleaf papers, of which rigidity or weight is lower than that of the plate-shaped members, are alternately stacked, the plate-shaped members and the sheet materials can be more reliably removed one at a time.
In accordance with a first aspect of the present invention, there is provided a sheet feeder in which plate-shaped members and sheet materials in a state of being alternately stacked are taken out one by one, comprising: at least one sucker which adheres to the plate-shaped members and sheet materials due to negative pressure by being brought into contact with the plate-shaped members and sheet materials; a suction fan which operates at a position close to a sheet material disposed at the uppermost position and sucks in air in the vicinity of the surface of the sheet material; and an elevator which moves the sucker and the suction fan in directions of approaching and moving apart from the stacked plate-shaped members and/or sheet materials, to thereby raise a plate-shaped member and/or a sheet material, which is adhered to the sucker.
According to the present invention, a sucker and suction fan are provided. The sucker suction adheres to elevate the plate-shaped member and the sheet material. The suction fan draws in air in the vicinity of the surface of the sheet material for suction adherence to the sucker to thereby suction adhere to and raise the sheet material. Although the suction force of the suction fan is smaller than that of the sucker, the sheet material can be removed from an underlying plate-shaped member by suction from the fan in the vicinity of the surface of the sheet material.
By means of the above-described suction fan, the sheet material is reliably separated from the plate-shaped member and can be removed by suction adherence to the sucker.
In accordance with a second aspect of the present invention, there is provided a sheet feeder in which plate-shaped members and sheet materials in a state of being alternately stacked are taken out one by one, comprising: a pair of side plates; a suction portion which is supported between the side plates in a movable manner in a direction perpendicular to the plate-shaped members and/or the sheet materials placed in a stack, and adheres to the plate-shaped members and/or sheet materials due to negative pressure; a suction device which is supported between the side plates in a movable manner in a direction perpendicular to the plate-shaped members and/or the sheet materials placed in a stack, and when the sheet material is disposed at the uppermost position, the suction device being operated at a position adjacent to the sheet material and sucking in air in the vicinity of the surface of the sheet material; an elevator which moves the suction portion and the suction device in a direction perpendicular to the plate-shaped members and/or the sheet materials placed in a stack to thereby elevate a plate-shaped member and/or a sheet material, stuck to the suction portion; and a sensor which is provided between the side plates so as to be movable in a direction substantially parallel to a direction in which the suction portion is movable, and detects and determines a state in which the suction portion and the plate-shaped member and/or sheet material contact each other.
In the present invention, preferably, when the sheet material is disposed at the uppermost position, the suction fan is operated in a state of being moved close to the sheet material, and thereafter, negative pressure is applied for the sucker at a predetermined timing to allow the sucker to adhere to the sheet material.
According to the aforementioned, in order to allow suction of the sheet material, first, the suction fan is operated to raise the sheet material from the plate-shaped member. Thereafter, the sheet material is suction adhered to the sucker. Since the suction force of the suction fan is smaller than that of the sucker, there is reduced the possibility of suction adhering the plate-shaped member together with the sheet material, and only the sheet material is lifted.
As a result, the sheet material is adhered to the sucker in a state in which the sheet material and the plate-shaped member closely contact each other. Therefore, the plate-shaped member is prevented from being sucked together with the sheet material, and only the uppermost sheet material can reliably be removed from an underlying plate-shaped member.
Further, in the present invention, preferably, the suction fan is operated in a state in which the sucker is brought into contact with the sheet material.
According to the aforementioned, with the sucker brought into contact with the sheet material, the suction fan is operated at the position in which for example, wind force of the suction fan applied onto the sheet material becomes maximum, to partially raise the sheet material. Subsequently, the sheet material is removed from an underlying plate-shaped member, and thereafter, the sheet material is suction adhered to the sucker.
At this time, preferably, the sucker and suction fan are moved so that the sheet material is separated from the plate-shaped member, and the sheet material is moved upward away from the plate-shaped member. Thereafter, the sheet material is suction adhered to the sucker by suction.
Moreover, in the present invention, preferably, the suction fan is provided so as to face one end of the sheet material.
According to the aforementioned, the suction fan is disposed so as to face an end, such as a peripheral edge, of the sheet material. As a result, the sheet material can more easily be separated from the plate-shaped member due to the suction force of the suction fan.
Still further, in the present invention, preferably, the suction fan is provided in the proximity of at least one of the suckers.
According to the aforementioned, the suction fan and the sucker are disposed adjacent to each other, and a region of the sheet material raised by the suction fan is suction adhered to the sucker. As a result, only the sheet material can be reliably lifted away from an underlying plate-shaped member.
In accordance with a third aspect of the present invention, there is provided a sheet feeding method in which first materials having high rigidity and second materials having flexibility in a state of being alternately stacked are taken out one by one from a magazine, comprising the steps of: (a) making a determination as to whether a material disposed at the uppermost position of the stacked materials is the first material or the second material; (b) when it is determined that the second material is disposed at the uppermost position, causing at least one sucker to abut against the uppermost material; (c) sucking in air in the vicinity of the surface of the uppermost material by a suction device; (d) moving the suction device upward by a small distance to separate the uppermost material from the stacked materials; (e) feeding negative pressure for the sucker to cause the sucker to adhere to the uppermost material; (f) stopping operation of the suction device; (g) moving upward the sucker and the suction device to completely separate the uppermost material from the stacked materials; (h) delivering the adhered uppermost material to a conveying portion; and (i) stopping application of negative pressure for the sucker.